The present invention relates to a polishing composition used in polishing the edge of a wafer for semiconductor devices and a polishing method using the same.
The edge of a wafer cut out from an ingot is generally beveled in a beveling process, then polished in an edge polishing process. This series of processes on the edge of the wafer is mainly intended to suppress occurrence of chipping on the edge of the wafer and to suppress formation of edge crown in epitaxial growth on the wafer.
The polishing composition used in the edge polishing process generally contains abrasives, such as silicon dioxide. The polishing composition splashes onto the surface of a wafer in edge polishing, and abrasives contained in the splashed polishing composition remain on the wafer in the form of dry gel. The remaining abrasives cause scratches on the surface of the wafer.
Japanese Laid-Open Patent Publication No. 11-349925 and Japanese Laid-Open Patent Publication No. 2000-158329 disclose an improved polishing composition for the edge polishing process. The improved polishing composition contains a water-soluble polymer, and the water-soluble polymer improves the wettability of the surface of a wafer to suppress remaining of abrasives in the form of dry gel on the wafer. However, even if the improved polishing composition is used, the amount of remaining abrasives on the wafer is not sufficiently reduced.